This study looks at combining two drugs, silevertinib and temozolomide, to treat newly diagnosed glioblastoma (GBM), a type of brain cancer. **Silevertinib** is designed to block signals that help cancer grow. **Temozolomide** damages the cancer cell's DNA, which can stop the growth of tumors. The study wants to know if using both together is better than temozolomide alone.

The study has two parts. In Part 1, 12 people will try both drugs to find the best dose and check safety. In Part 2, 150 people will be randomly chosen to receive either both drugs or just temozolomide. The treatment is given in 28-day cycles, with temozolomide taken for the first 5 days of each cycle.

If you join, you will need to visit the clinic often for check-ups and tests. You will also keep a diary at home to track when you take the medicine.

• The study lasts for several months with frequent clinic visits.
• Participants will take the drugs orally and record their intake.
• Eligibility includes having GBM and completing surgery and radiation.